It does seem correct that the project hasn't been abandoned, but management is in a critical state right now. If there have been updates, even if they are not critical, a new stable release should be pushed.

Things are worse on the NuGet side. There are no indications that "control" has passed to any other individuals, yet a separate fork of the project on GitHub is being used as the latest release version (1.9.2) for NuGet. This is problematic for several
reasons, not the least of which is that DotNetZip.semverd 1.9.2 is unsigned since the snk for the project is not shared. It would be a shame to see such a stable and useful piece of OSS drift into obscurity because of mismanagement.